* Bump Raspberry Pi kernel to 5.4
Bump kernel to the downstream Raspberry Pi 5.4 kernel. Drop patches
already merged upstream and use rebased patches for USB reset
controller (required for U-Boot 2020.10 for USB SSD boot).
* Add compatible node for upstream U-Boot
Add brcm,bcm2835-pl011 to make upstream U-Boot bind with the
bcm283x_pl011 driver. This allows to boot with the device tree provided
by the Raspberry Pi Linux kernel 5.4 even without enable_uart=1.